Combined tank support and tie down means for a ship or the like

ABSTRACT

A unique combined tank support and tie down structure on a tank in a ship or the like for transporting low temperature liquid, comprising load supporting insulation at the ship&#39;&#39;s bottom, the tank supported at its bottom on the insulation, rigid tie down attachment structure fixed to a lower outer surface of the tank adjacent the bottom thereof, a plurality of substantially vertically oriented, individual, spaced apart tie down rods or bolts or the like attached to the attachment structure and to a bottom structure of the ship to prevent vertical upward movement of the tank relative to the ship, and a plurality of cooperating tank support members connected to the attachment structure and to a bottom structure of the ship enabling radial expansion and contraction of the tank and attachment structure relative to the ship and preventing movement of the tank in a plane parallel with the ship&#39;&#39;s bottom.

United States Patent Murphy [75] Inventor: John C. Murphy, Pittsburgh, Pa,

[73] Assignees: Pittsburgh Des Moines Steel Company, Pittsburgh, Pa; Gaz Transport, Paris, France; part interest to each [22] Filed: Jan. 10, 1974 [21] Appl No; 432,237

[52] US. Cl. ll4/74 A; 220/15 [51] Int. Cl B63b 25/14; B63b 3/26 [58] Field of Search 114/72-73, 114/74 12,74 T, 74 A. 75; 220/9 A, 9 LG, 15', 62/45, 55

[56] References Cited UNITED STATES PATENTS 3,025,993 3/1962 Horton et al. 220/15 3,071,094 H1963 Lcroux ll4/74A 3,273,740 9/1966 Herrenschmidt.., 220/15 3.425.583 2/1969 Bridges .1 ll4/74 A 3,459,148 8/1969 Progler et a1, 114/74 A 1 July 15, 1975 Primary E.\'uminer-Trygve M, Blix Assistant Examiner.lesus Dv Sotelo Armrney, Agent, or FirmShoemaker and Mattare [57] ABSTRACT A unique combined tank support and tie down structure on a tank in a ship or the like for transporting low temperature liquid, comprising load supporting insulation at the ships bottom, the tank supported at its bottom on the insulation, rigid tie down attachment structure fixed to a lower outer surface of the tank adjacent the bottom thereof, a plurality of substantially vertically oriented, individual, spaced apart tie down rods or bolts or the like attached to the attachment structure and to a bottom structure of the ship to prevent vertical upward movement of the tank relative to the ship, and a plurality of cooperating tank support members connected to the attachment structure and to a bottom structure of the ship enabling radial expansion and contraction of the tank and attachment structure relative to the ship and preventing movement of the tank in a plane parallel with the ships bottom.

20 Claims, 10 Drawing Figures COMBINED TANK SUPPORT AND TIE DOWN MEANS FOR A SHIP OR THE LIKE BACKGROUND OF THE INVENTION This invention relates to a unique tank support and tie down means on a tank in a ship or the like for transporting low temperature liquid. In particular. the present invention relates to a means for supporting and securing in position a tank for containing low temperature liquids such as liquid natural gas and the like for transport on a ship or like structure and wherein the tank support and tie down means enables thermal expansion and contraction of the tank but prevents vertical upward movement of the tank relative to the ship and also prevents horizontal shifting movement of the tank relative to the ship.

In accordance with the present invention. the tie down and support structure for the tank is connected to the tank adjacent the bottom thereof and accordingly, is at the strongest portion of the ship and does not exert loads on the side ofthe tank or on the sides of the hulls of the ship, which loads might cause buckling of either the tank or the ships sides. Moreover. by attachment of the tie down and support means to a lower por tion of the tank most of the vertical expansion or contraction of the tank due to thermal changes occurs above the point of attachment of the tie down and support means and thereby small thermal stresses are induced in said means.

With the tie down and support means of the present invention, the support means is positioned relative to an attachment structure on a lower outer surface portion of the tank to withstand vertical compressive load ing imposed thereon from the weight of the side wall of the tank and from the weight of a portion of the stored liquid in the tank adjacent the side wall thereof and at the same time the support means includes relatively slidable portions which enable expansion and contraction of the tank in a radial direction but which prevent movement of the tank in a horizontal direction. The tie down means effectively resists overturning or upward movement of the tank relative to the ship and also can be used to exert a downward preload of the tank onto the load supporting insulation at the ships bottom.

Further, the unique combined tank support and tie down means on the tank has means enabling drainage of any leaked liquid from the tank past the attachment means for the tie down and support structure and to a sump or other suitable point as desired.

OBJECTS OF THE INVENTION It is an object of this invention to provide a combined tank support and tie down means on a tank in a ship or the like for transporting low temperature liquid wherein the combined tank support and tie down means includes tank support members at a lower portion of the tank which enable radial expansion and contraction of the tank relative to the ship but which prevent horizontal movement or shifting of the tank relative to the ship and at the same time provide a vertical support for the side walls of the tank and for a portion of the liquid stored within the tank, and said combined tank support and tie down means further including tie down means connected between the attachment of said support members with said tank and a bottom structure of the ship for holding the tank downwardly against tilting or vertical upward movement.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a view in elevation with portions shown in section of a ship including a plurality oftanks and insulation and support means in accordance with the invention;

FIG. 2 is a plan view ofthe ship and tanks of FIG. I;

FIG. 3 is a greatly enlarged perspective view with portions broken away of one form of unique tank support and tie down means according to the present invention;

FIG. 4 is an enlarged transverse sectional view of a ship as in FIGS. I or 2, with portions broken away. of a tank with the unique tank support and tie down means of the present invention in a ship;

FIG. 5 is a greatly enlarged fragmentary sectional view of the tank support and tie down means and a portion of the tank and ship of FIG. 4;

FIG. 6 is a greatly enlarged view in elevation of a modified tank support and tie down means in accordance with the invention;

FIG. 7 is a horizontal sectional view of a tank and combined support and tie down means in accordance with the invention with portions broken away;

FIG. 8 is an enlarged perspective fragmentary view similar to FIG. 3 of the modified tank support and tie down means of FIG. 6;

FIG. 9 is an enlarged fragmentary transverse sectional view of a modified tank and ship construction utilizing the tank support and tie down means of the present invention;

FIG. 10 is a longitudinal sectional view of the modified form of the invention of FIG. 9.

DETAILED DESCRIPTION OF THE INVENTION In the drawings. wherein like reference numerals in dicate like parts throughout the several views. a ship S includes a bottom 8. opposite side walls C and D and a plurality of spaced apart transverse bulkheads or walls W subdividing the interior of the ship S into a plu rality of holds H in which are supported a plurality of tanks T. each tank surrounded by insulation I.

Each tank T is securely held in position in its respective hold H by means of a unique combined tank support and tie down 10 which comprises an attachment means II fixed to a lower outer surface portion of the tank T. a radially slidable tank support 12 engaged between the underside of the attachment 1 I and a portion of the ships bottom and a tie down 13 connected be tween the attachment and the ships bottom to hold the tank downwardly in the hold of the ship.

The tank preferably includes a semi-spherical upper portion 0 extending over substantially the upper half of the tank. a cylindrical sid wall portion h. a knuckle portion c connecting the cylindrical side wall portion b with a conical bottom d and a part spherical lower end or cap e. Suitable insulation such as perlite or the like surrounds the cylindrical side wall b and semi-spherical upper portion a and a suitable load-bearing insulation of any suitable type such as plastic foam or perlite-filled plywood boxes or the like 14 is provided at the bottom of the ship and the conical bottom of the tank rests on and is supported by the load-bearing insulation I4.

A pair of spaced apart splash shields 15 and 16 made of a material such as aluminum foil or the like extend through the insulation I in substantial conformity with the contour of the cylindrical and semi-spherical portions of the tank to prevent any liquid which may leak from the tank from reaching the ships structure. Glass fiber insulation blankets are provided between the two splash shields l5 and 16 and between the inner splash shield and the tank T. The load-bearing insulation 14 at the ship's bottom is supported on an inner bottom portion or tank support platform or foundation 17 in the ship's bottom.

The unique combined tank support and tie down means 10 is secured to the knuckle portion c of the tank between the insulation 1 and load supporting insulation 14 at the side and bottom. respectively. of the ship. The attachment means 11 includes an annular, substantially continuous plate or ring 18 welded at an inner edge 19 thereof to the outer surface of the tank and the inner edge 19 has a plurality of notches or re cesses 20 therein through which any leaked liquid is enabled to drain past the plate 18. A similar but substantially wider continuous annular plate 21 is welded at an inner edge 22 thereof to the outer surface of the tank spaced below the point of attachment of upper plate 18. and plate 21 also has a plurality of drain openings or passages 23in the inner edge 22 thereof for drainage of any leaked liquid therepast. A vertically extending annular wall 24 is welded at its upper and lower edges to the plates 18 and 21, respectively, and a plurality of radially extending vertically oriented plates 25 are also welded at their upper and lower edges to the plates 18 and 21 radially outwardly of wall 24 and the plates 25 are also welded at their inner edges to the outer surface of wall 24. The outer edges of upper and lower walls or plates 18 and 21 are in substantial vertical alignment.

A tank support means 12 includes a plurality of circumferentially spaced apart. radially extending. inverted channel-shaped guide means or keyways 26 welded or otherwise suitably fixed to the bottom surface of bottom plate 21 approximately medially of the inner and outer edges thereof. A plurality of similar, substantially vertically aligned channel-shaped guide means or keyways 27 are welded or otherwise suitably affixed on the upper surface of a radially outwardly extending horizontal portion 17 of the bottom support for the tank. A continuous annular support ring 28 is engaged between the upper and lower keyways 26 and 27 and comprises a substantially continuous, annular, vertically extending wall 29 having a pair of vertically spaced upper and lower annular rings 30 and 31 welded or otherwise suitably affixed to the upper and lower edges of the wall 29. The wall 29 has openings 32 therethrough at predetermined spaced intervals around the ring 28 to enable inspection of the support and detection of any leakage inwardly of the ring 28. The ring 28 is keyed to the keyways 26 and 27 by means ofa plurality of upper and lower keys or lugs 33 and 34, respec tively. welded or otherwise suitably affixed to the upper surface of upper plate 30 and to the lower surface of lower plate 31 and in alignment with the channelshaped keyways 26 and 27, respectively. Substantially vertically oriented, radially extending reinforcing plates 35 and 36 are welded between upper and lower plates 30 and 31 on opposite sides of ring 29 in substan' tial vertical alignment with the channel-shaped keyways 26 and 27.

The tie down means 13 includes a substantially continuous annular ring 37 suitably affixed as by welding or the like to a substantially vertical wall 38 of the ship's inner bottom or tank support structure. and

spaced vertically downwardly from the substantially horizontal portion 17 of the support framework for the tank. A plurality of radially extending gusset plates 39 are welded between the plate or ring 37 and the wall 38 to brace the ring 37, and a plurality of spaced apart, substantially vertically oriented tie down bolts 40 extend at their opposite ends through aligned openings in the ring 37 and in the outer edge of bottom plate 21 of attaching means 10. Heavy hex nuts or the like 4] and 42 are threaded onto the upper and lower threaded ends. respectively, of the bolts 40 and spherical washer assemblies 43 and 44 are engaged between the hex nuts and the respective plates so that upon radial movement of the plate 21 and the associated upper end of the bolts 40, the bolts are enabled to assume an inclined position without imparting bending forces thereon.

An upward convex insulation retainer 45 is suitably affixed at its opposite longitudinal edges between the side D of the ship and the outer edge of upper plate 18 of attaching means 10 to retain the perlite insulation l in position. Suitable insulation means such as fiberglass blanket or the like 46 is suitably attached to the underside of retainer 45 and extends downwardly along side the attaching means 11. Similarly, spaced inwardly from the support 12 are a plurality oflayers of fiberglas insulation 47 with a splash shield 48 interposed between two of the layers of insulation and a secondary barrier 49 preferably made of aluminum or the like to confine any liquid which leaks from the tank and drains downwardly through the drain holes 20 and 23 in the plates 18 and 21 to the space between the shields and the outer surface of the tank so that the liquid will not contact portions of the ship's structure but will instead be drained downwardly between the secondary barrier 49 and the tanks outer surface to a sump or other suitable means at the bottom of the tank from whence the leaked liquid may be pumped to a suitable location. A circumferentially extending gas detection manifold 50 is disposed in the space radially inwardly of support 12 and above the horizontal portion 17 of tank support framework and outwardly of the insulation 47 to detect the presence of any gas in this space.

Thus, the support 12 and its associated keyways 26 and 27 enable radial movement of the tank and attaching means 10 due to thermal expansion and contraction of the tank but prevent horizontal movement of the tank relative to the ship, or in other words, prevent bodily movement of the tank in a plane parallel to the ships bottom. In other words, each pair of channels 26 and 27 is radially disposed and thus permits radial movement but prevents movement in a tangential direction relative to the tank, and the spacing of these keyways around the circumference of the tank accordingly prevents any horizontal movement of the tank relative to the ship. Moveover, the tie down bolts 40 hold the tank downwardly against any up lift forces thereon due either to vapor pressure within the tank or to rolling or pitching motion of the ship in which the tank is supported. The tie down bolts 40 do not take any compressive loading since all of the compressive loading is absorbed by the tank support 12 and the tanks bottom which rests on the load-bearing insulation 14.

A modified tank wupport 12' as seen in FIGS. 6 and 8 includes the upper attachment 11 as previously described and the horizontal portion 17 of the tank support frame and a vertical wall 38 and annular ring 37 with the tie down bolts 40 extended between the ring 37 and the lower ring or plate 21 of attachment means ll, all as previously described. However. rather than a continuous annular support ring 12 as previously described. the tank support 12' in these figures includes a plurality of separate tank support members or pedestals 51. The support members or pedestals 51 each includes an upper wall 52 and a spaced lower wall 53 of greater length than the upper wall 52. A pair of inclined side walls 54 and 55 are fixed as by welding or the like at their upper and lower ends to the upper plate 52 and lower plate or wall 53, respectively. thus forming a substantially trapezoidal shape. A center web or plate 56 having an outline corresponding to the outline of the upper. lower and side walls is suitably welded to the inner surfaces of the upper. lower and side walls to reinforce the pedestal 51 and a pair of brace or reinforcing plates 57 are welded to opposite sides of the web 56 in substantial alignment with the key or slide block 33 which is welded to the upper surface of upper wall or plate 52 and is slidably received within the channelshaped keyway 26 secured to the underside of plate 21 of the attachment means I]. A plurality of bolts or the like 58 extend through the lower wall or plate 53 into the horizontal portion l7 to thus rigidly and immovably fix the lower end of the support pedestal to the support frame or platform for the tank. Thus. the pedestal is not enabled to move relative to the ship but because of the keyway at the upper end thereof and upon which the attachment means is slidably supported. the tank and attachment means are enabled to move radially relative to the support and the tank is prevented from horizon tal movement relative to the ship just as in the previously described form of the invention.

In this form of the invention as well as in the form of the invention in FIGS. 1 through 5, a suitable bearing means 59 is interposed between the channel or keyway 26 and the slide block or key 33 and also between the keyway 27 and the keys 34 for reducing friction between these parts and also the bearing means preferably has a heat insulating characteristic such as to reduce or prevent heat transfer through the keyways. An example of a suitable bearing material is a treated wood known as Permali type EH62.

In FIGS. 9 and 10, a modified form of the invention is illustrated and in this form of the invention the tie down and support means is substantially identical to that previously described. However, in this form of the invention rather than having conical bottom 2 as in FIG. 4, the tank has a substantially flat bottom a and is supported on a substantially planar load supporting insulation 14' supported on the ships bottom B rather than on the tank supporting platform or foundation I7 as in FIG. 4. The tie down and support means is anchored to a suitable built-up structure or support 17 rather than to a horizontally extending portion 17 of a tank support or foundation as in the previous form of the invention.

In a specific example of the invention, the plates 18 and 21 of the attachment means comprise aluminum and are approximately 2 inches thick and the wall or plate 24 extending between the upper and lower plates 18 and 21 also comprises aluminum and is approximately 1 inch thick as are the radial, vertically oriented reinforcing plates 25. The upper keyway 26 in the form of the invention of FIGS. 4 and 5 comprises aluminum but the lower keyway 27 comprises carbon steel. The keys 33 and 34 on the support ring 28 comprise 9 percent nickel steel alloy and the reinforcing plates 35 and 36 are approximately one-half inch thick and comprise a 9 percent nickel steel alloy and are spaced approximately 4 inches apart.

Moreover, the keyways and associated keys 26 and 33 are spaced apart approximately 4 feet 7% inches center to center. and in the installation of a tank having the combined support and tie down means of the present invention approximately every fifth one of the plates is omitted until after a hydro test is performed on the tank.

While the tank support and tie down means is specifically shown and described herein as attached to the knuckle portion of the tank. the tank support and attachment means could be attached to a different portion of the tank. such as the cylindrical portion. for example. and the tank could have any other suitable size and shape rather than that shown. if desired.

As this invention may be embodied in several forms without departing from the spirit or essential character istics thereof. the present embodiment is therefore illustrative and not restrictive. since the scope of the invention is defined by the appended claims rather than by the description preceding them. and all changes that fall within the metes and bounds of the claims or that form their functional as well as conjointly cooperative equivalents. are therefore intended to be embraced by those claims.

What is claimed is:

l. A unique combined tank support and tie down means on a tank in a ship or the like for transporting low temperature liquid comprising. load supporting insulation means at the ships bottom. said tank supported at its bottom on said load supporting insulation means. rigid, annular. circumferentially extending tie down attaching means fixed to a lower outer surface of said tank adjacent the bottom thereof and extending about the tank. a plurality of substantially vertically oriented, individual. spaced apart. elongate tie down means having upper and lower ends and attached at their upper ends to said attaching means and attached at their bottom ends to a bottom structure of the ship, thus preventing vertical upward movement of the tank relative to the ships bottom, and a plurality of substantially similar tank support means spaced apart around the circumference of the tank and connected to the attaching means and to the ships bottom structure, said tank support means comprising substantially horizontal guide means on the attaching means extending radially relative to the tank. and support means disposed between the guide means and the ship's bottom structure and relatively slidably engaged with the guide means to support the tank and to enable radial movement of the tank and attaching means relative to the ship's bottom due to thermal expansion and contraction of the tank and to prevent bodily movement of the tank in a direction parallel to the ships bottom.

2. A combined tank support and tie down means as in claim I, wherein the attaching means comprises an annular, horizontally extending plate fixed at an inner edge thereof to a lower outer surface portion of the tank, said elongate tie down means attached at their upper ends to the plate.

3. A combined tank support and tie down means as in claim 2, wherein the guide means include keyway means fixed to the underside of said annular plate and said support means comprises a support member sup- 4. A combined tank support and tie down meansas in claim 3, wherein further keyway means are on the bottom structure of the ship and said support member is engaged with said further keyway means, the annular plate ofthe attaching means being thus radially slidable relative to the support member and the support member being radially slidable relative to the bottom structure of the ship.

5. A combined tank support and tie down means as in claim 3, wherein the support member is fixed relative to the bottom structure of the ship.

6. A combined tank support and tie down means as in claim 2, wherein the guide means include keyway means fixed to the underside of the annular plate and a plurality of support members supported on a bottom structure of the ship and engaged with said keyway means on the underside of the annular plate.

7. A combined tank support and tie down means as in claim 6, wherein the support members are fixed to the bottom structure of the ship.

8. A combined tank support and tie down means as in claim 7, wherein the support members are circumferentially spaced apart substantially equally around the circumference of the tank.

9. A combined tank support and tie down means as in claim 1, wherein the attaching means includes a pair of upper and lower annular. vertically spaced apart plates having inner and outer edges and upper and lower surfaces and fixed at the inner edges to vertically spaced locations on an outer, bottom portion of the tank, the outer edges of the plates in substantial vertical alignment. and brace means fixed to the confronting surfaces of the plates to reinforce the attaching means.

10. A combined tank support and tie down means as in claim I, wherein the attaching means include an an nular, horizontal plate having an outer edge and an inner edge and fixed at its inner edge to an outer bottom portion of the tank, a plurality of radially extending keyways on the underside of said plate, said support means supported on a bottom structure of the tank in substantial vertical alignment with said plate and a plurality of keys on said support means engaged with the keyways on said plate.

11. A combined tank support and tie down means as in claim 10, wherein a plurality of keyways are on the bottom structure of the ship in substantial vertical alignment with the keyways on the plate, and a plurality of keys are on a bottom portion of the support means engaged with said keyways on said bottom structure.

12. A combined tank support and tie down means as in claim 10, wherein the support means is fixed to the bottom structure of the ship.

13. A combined tank support and tie down means as in claim 9, wherein the support means includes a continuous, annular support ring having upper and lower surfaces. radially extending, spaced apart keys on the upper and lower surfaces of the support ring, and a plurality of radially extending keyways on the lower surface of the lower plate of the attaching means and on the ship's bottom structure, said keys on said support ring slidably engaged in said keyways.

M. A combined tank support and tie down means as in claim 13, wherein said tie down means includes a plurality of circumferentially spaced apart elongate bolts having threaded upper and lower ends received through holes in the bottom plate of the attaching means and in the ships bottom structure, respectively, and nuts threaded onto said threaded ends to securely hold said tank downwardly against said load supporting insulation.

15. A combined tank support and tie down means as in claim 1, wherein the tank has a substantially conically shaped bottom and the load supporting insulation is shaped complemental to the bottom of the tank.

16. A combined tank support and tie down means as in claim 1, wherein the bottom of the tank is substantially flat, and the load supporting insulation is shaped complemental to the bottom of the tank.

17. A combined tank support and tie down means as in claim 14, wherein the inner edges of said upper and lower plates of said attaching means have drain notches therein for drainage therepast of any liquid which leaks from the tank.

18. A combined tank support and tie down means as in claim 17, wherein splash shields are positioned around said tank in outwardly spaced relationship thereto to confine to the space between the splash shields and the outer surface of the tank any liquid which leaks from the tank.

19. A combined tank support and tie down means as in claim 18, wherein heat insulating bearing means is engaged between the keys and keyways to reduce heat transfer through the keyway means.

20. A unique combined tank support and tie down means on a tank in a ship or the like for transporting low temperature liquid comprising, load supporting insulation means at the ships bottom, said tank supported at its bottom on said load supporting insulation means, rigid tie down attaching means fixed to a lower outer surface of said tank adjacent the bottom thereof and extending about the tank, said tie down attaching means including a pair of upper and lower annular, vertically spaced apart plates having inner and outer edges and upper and lower surfaces and fixed at the inner edges to vertically spaced locations on an outer, bottom portion of the tank, the outer edges of the plates in substantial vertical alignment, and brace means fixed to the confronting surfaces of the plates to reinforce the attaching means, a plurality of substantially vertically oriented, individual, spaced apart, elongate, tie down bolts having threaded upper and lower ends received through holes in the lower plate of the attaching means and in the ships bottom structure, respectively, and nuts threaded onto said threaded ends to securely hold said tank downwardly against said load supporting insulation, and a continuous annular support ring having upper and lower surfaces, radially extending spaced apart keys on the upper and lower surfaces of the support ring, and a plurality of radially extending keyways on the lower surface of the lower plate of the attaching means and on the ship's bottom structure, said keys on said support ring slidably engaged in said keyways so as to enable radial movement of the tank and attaching means due to thermal expansion and contraction of the tank and to prevent horizontal movement of the tank relative to the ship, the inner edges of said upper and lower plates of said attaching means having drain notches therein for drainage therepast of any liquid which leaks from the tank, splash shields positioned around said tank in outwardly spaced relationship thereto to confine to the space between the splash shields and the outer surface of the tank any liquid which leaks from the tank, and heat insulation bearing means engaged between the keys and keyways to reduce heat transfer through the keyway means.

a awwaa -aa "4.... w as 

1. A unique combined tank support and tie down means on a tank in a ship or the like for transporting low temperature liquid comprising, load supporting insulation means at the ship''s bottom, said tank supported at its bottom on said load supporting insulation means, rigid, annular, circumferentially extending tie down attaching means fixed to a lower outer surface of said tank adjacent the bottom thereof and extending about the tank, a plurality of substantially vertically oriented, individual, spaced apart, elongate tie down means having upper and lower ends and attached at their upper ends to said attaching means and attached at their bottom ends to a bottom structure of the ship, thus preventing vertical upward movement of the tank relative to the ship''s bottom, and a plurality of substantially similar tank support means spaced apart around the circumference of the tank and connected to the attaching means and to the ship''s bottom structure, said tank support means comprising substantially horizontal guide means on the attaching means extending radially relative to the tank, and support means disposed between the guide means and the ship''s bottom structure and relatively slidably engaged with the guide means to support the tank and to enable radial movement of the tank and attaching means relative to the ship''s bottom due to thermal expansion and contraction of the tank and to prevent bodily movement of the tank in a direction parallel to the ship''s bottom.
 2. A combined tank support and tie down means as in claim 1, wherein the attaching means comprises an annular, horizontally extending plate fixed at an inner edge thereof to a lower outer surface portion of the tank, said elongate tie down means attached at their upper ends to the plate.
 3. A combined tank support and tie down means as in claim 2, wherein the guide means include keyway means fixed to the underside of said annular plate and said support means comprises a support member supported on a bottom structure of the ship and engaged with the keyway means on the underside of said annular plate.
 4. A combined tank support and tie down means as in claim 3, wherein further keyway means are on the bottom structure of the ship and said support member is engaged with said further keyway means, the annular plate of the attaching means being thus radially slidable relative to the support member and the support member being radially slidable relative to the bottom structure of the ship.
 5. A combined tank support and tie down means as in claim 3, wherein the support member is fixed relative to the bottom structure of the ship.
 6. A combined tank support and tie down means as in claim 2, wherein the guide means include keyway means fixed to the underside of the annular plate and a plurality of support members supported on a bottom structure of the ship and engaged with said keyway means on the underside of the annular plate.
 7. A combined tank support and tie down means as in claim 6, wherein the support members are fixed to the bottom structure of the ship.
 8. A combined tank support and tie down means as in claim 7, wherein the support members are circumferentially spaced apart substantially equally around the circumference of the tank.
 9. A combined tank support and tie down means as in claim 1, wherein the attaching means includes a pair of upper and lower annular, vertically spaced apart plates having inner and outer edges and upper and lower surfaces and fixed at the inner edges to vertically spaced locatIons on an outer, bottom portion of the tank, the outer edges of the plates in substantial vertical alignment, and brace means fixed to the confronting surfaces of the plates to reinforce the attaching means.
 10. A combined tank support and tie down means as in claim 1, wherein the attaching means include an annular, horizontal plate having an outer edge and an inner edge and fixed at its inner edge to an outer bottom portion of the tank, a plurality of radially extending keyways on the underside of said plate, said support means supported on a bottom structure of the tank in substantial vertical alignment with said plate and a plurality of keys on said support means engaged with the keyways on said plate.
 11. A combined tank support and tie down means as in claim 10, wherein a plurality of keyways are on the bottom structure of the ship in substantial vertical alignment with the keyways on the plate, and a plurality of keys are on a bottom portion of the support means engaged with said keyways on said bottom structure.
 12. A combined tank support and tie down means as in claim 10, wherein the support means is fixed to the bottom structure of the ship.
 13. A combined tank support and tie down means as in claim 9, wherein the support means includes a continuous, annular support ring having upper and lower surfaces, radially extending, spaced apart keys on the upper and lower surfaces of the support ring, and a plurality of radially extending keyways on the lower surface of the lower plate of the attaching means and on the ship''s bottom structure, said keys on said support ring slidably engaged in said keyways.
 14. A combined tank support and tie down means as in claim 13, wherein said tie down means includes a plurality of circumferentially spaced apart elongate bolts having threaded upper and lower ends received through holes in the bottom plate of the attaching means and in the ship''s bottom structure, respectively, and nuts threaded onto said threaded ends to securely hold said tank downwardly against said load supporting insulation.
 15. A combined tank support and tie down means as in claim 1, wherein the tank has a substantially conically shaped bottom and the load supporting insulation is shaped complemental to the bottom of the tank.
 16. A combined tank support and tie down means as in claim 1, wherein the bottom of the tank is substantially flat, and the load supporting insulation is shaped complemental to the bottom of the tank.
 17. A combined tank support and tie down means as in claim 14, wherein the inner edges of said upper and lower plates of said attaching means have drain notches therein for drainage therepast of any liquid which leaks from the tank.
 18. A combined tank support and tie down means as in claim 17, wherein splash shields are positioned around said tank in outwardly spaced relationship thereto to confine to the space between the splash shields and the outer surface of the tank any liquid which leaks from the tank.
 19. A combined tank support and tie down means as in claim 18, wherein heat insulating bearing means is engaged between the keys and keyways to reduce heat transfer through the keyway means.
 20. A unique combined tank support and tie down means on a tank in a ship or the like for transporting low temperature liquid comprising, load supporting insulation means at the ship''s bottom, said tank supported at its bottom on said load supporting insulation means, rigid tie down attaching means fixed to a lower outer surface of said tank adjacent the bottom thereof and extending about the tank, said tie down attaching means including a pair of upper and lower annular, vertically spaced apart plates having inner and outer edges and upper and lower surfaces and fixed at the inner edges to vertically spaced locations on an outer, bottom portion of the tank, the outer edges of the plates in substantial vertical alignment, and brace means fixed to the confronting surfaces of the plates to reinforce the attAching means, a plurality of substantially vertically oriented, individual, spaced apart, elongate, tie down bolts having threaded upper and lower ends received through holes in the lower plate of the attaching means and in the ship''s bottom structure, respectively, and nuts threaded onto said threaded ends to securely hold said tank downwardly against said load supporting insulation, and a continuous annular support ring having upper and lower surfaces, radially extending spaced apart keys on the upper and lower surfaces of the support ring, and a plurality of radially extending keyways on the lower surface of the lower plate of the attaching means and on the ship''s bottom structure, said keys on said support ring slidably engaged in said keyways so as to enable radial movement of the tank and attaching means due to thermal expansion and contraction of the tank and to prevent horizontal movement of the tank relative to the ship, the inner edges of said upper and lower plates of said attaching means having drain notches therein for drainage therepast of any liquid which leaks from the tank, splash shields positioned around said tank in outwardly spaced relationship thereto to confine to the space between the splash shields and the outer surface of the tank any liquid which leaks from the tank, and heat insulation bearing means engaged between the keys and keyways to reduce heat transfer through the keyway means. 